Electronic pulse shaping circuit



March 1, 1949. I J. 1;. RECTOR 2,462,897

ELECTRONIC PULSE SHAPING CIRCUIT Filed Oct. 3, 1944 INVENTOR. JACOB L.RECTOR ATTORNEY Patented Mar. 1, 1949 UNITED STATES PATENT OFFICE(Granted under the act of March 3, 1883, as amended April 30, 1928; 3700. G. 757) 11 Claims.

The invention described herein may be manufactured and used by or forthe Government for governmental purposes, without the payment to me ofany royalty thereon.

This invention relates to electronic circuits particularly adaptable foruse as pulse or sweep generators, keyers, modulators and the like.

It is a principal object of the invention to provide a circuit for theaforementioned purposes which is relatively simple and flexible andwhich is largely independent of the impedance of the load fed by thecircuit.

For a detailed description of the invention, together with other andfurther objects thereof, reference is had to the following descriptiontaken in connection with the single figure of the drawing, which is acircuit diagram of one form of my invention.

In the drawing, tubes l and I2, which are preferably arc-discharge tubesof the Thyraton type, have their space-current paths from anode tocathode in parallel.

In series with both tubes is the space-current path of a vacuum tube 14,preferably one having high perveance and high emission. The anode oftube I4 is connected to the positive terminal of a space-current sourceIS, the negative terminal of which is grounded. I

The grid of the tube M can be biased at zero potential or biasedpositive with respect to its cathode by means of a voltage source l8connected between the grid and cathode through a relatively highresistance 20, so that the impedance of said tube is normally low.

Tubes I0 and I2 are normally maintained nonconducting by means ofnegative biases applied to their grids from voltage sources 22 and 24through relatively high resistances 26 and 28.

The load circuit 30 is connected to terminals 32 and 34 in the cathodecircuit of tube It], or it may be connected to terminals 36 and 38 inthe plate circuit of tube I4 by removing the short circuit across saidterminals, or load circuits can be connected at both points. Because thetube [0 is non-conducting, no current can flow through the load circuit.

The grid of tube ['0 is adapted to be intermittently rendered positiveby means of sharp positive pulses, such as shown at 4, from a keyingsource adapted to be connected to terminals 6 and 8. Each pulse issufficient to overcome the negative grid bias on tube In and render saidtube conducting so that plate current will flow through tubes Ill and i4and the load circuit 3!].

The potential drop across loadcircuit is now applied to the grid of tubel2 through an adjustable R-C circuit comprisin resistor 40 and condenser42. The output of this circuit is applied to the grid of tube I2 througha decoupling resistor 44 and blocking condenser 45. After a timeinterval, depending upon the time constant of 3-0 circuit 4ll42, saidgrid will be rendered sufficiently positive to overcome the negativebias from source 24 and render tube l2 conducting, whereby a pulse ofvoltage will be developed across resistor 46 in the cathode circuit oftube 12.

The voltage pulse across resistor 46 is now applied to a negative pulsegenerator 48 which will deliver a sharp pulse of negative voltage to thegrid of tube l4, thereby biasing it to cutofi and renderin itnon-conducting, whereby the plate current through tubes I0 and I2 andtheir load circuits will be interrupted and the voltage at their anodesreduced sufficiently to render them non-conducting. This cycle ofoperation is repeated at every positive pulse applied to the grid oftube [0.

Negative pulse generator 48 may take the form of a conventional blockingoscillator which is started by a positive pulse and which blocks itselfafter the first voltage cycle generated thereby. One example of suchblocking oscillator is described in Bedford Patent 2,358,297, issuedSeptember 19, 1944. In general, circuit 48 acts to amplify and invertthe pulse applied thereto from resistor 46, and any circuit which willperform this function can be used.

It will be seen that the character and duration of the pulses throughload circuit 30 will depend upon several factors. One factor is the timeconstant of the Rr-C circuit which can be adjusted to any desiredinterval by adjusting the value of resistor 40. Other factors are theionizing time of tube l2 and the starting time in pulse generator 48 andthe pulse duration of the output thereof. If the total time delay due toall the above factors is greater than the duration of input pulses 4 andless than the intervals therebetween, then there will occur a singlepulse through the load circuit for each input pulse 4. If the total timedelay is greater than the interval between input pulses, then there willbe one pulse in output circuit 30 for every two or more input pulses, inwhich case the network will act as a frequency divider. On the otherhand, if said time delay is less than the duration of each pulse 4, thenthere will be two or more pulses in output circuit 30 for each pulse inthe input. The latter feature makes it possible to generate groups ofoutput pulses for each pulse at the input, the numher in each groupdepending upon the duration of the input pulses and the time delayfactors above mentioned.

A particular feature of the circuit is the fact that the operation islargely independent of the impedance of the load 30, since the impedanceof tubes H! and [4 when they are conducting is relatively small comparedto the load impedance. Hence the voltage drop across said load and thetime operation of the succeeding circuits is substantially independentof the load impedance.

The pulse shape across load at will be substantially rectangular if saidload is resistive. Other pulse shapes can be derived by making said loadcircuit reactive or a combination of reactance and resistance. By makingload circuit 33 a constant charging circuit, the output wave will be asawtooth wave, the duration of which can be controlled by adjustin thetime constant of R-C circuit 40-42.

Other uses and features will be obvious to those skilled in the art, andit is aimed in the appended claims to cover all changes andmodifications as fall within the true spirit and scope of the invention.

I claim:

1. An electronic circuit comprising at least first, second and thirdgrid-controlled electron tubes, said first and second tubes having theirspace-current paths connected in parallel and connected to a'source ofspace-current in series with the space-current path of said third tube,an impedance in the cathode circuit of said second tube, said first andsecond tubes being normally non-conducting arc-discharge tubes, meanstorender said first tube conducting, whereby space-current will flowthrough said firstand third tubes, an adjustable time delay circuit fortransmitting the output of said first tube to the grid of said secondtube and render it conducting whereby space-current will flow throughsaid impedance, and means responsive to current flow in said impedanceto render said third tube non-conductin thereby interruptingthe'space-current flow through all of said tubes.

2. An electronic circuit comprising at least first, second and thirdgrid-controlled electron tubes, said first and second tubes having theirspace-current paths connected in parallel and connected to a source ofspace-current in series with the space-current path of said third tube,a load circuit connected in the cathode circuit of said first tube, aresistor in the cathode circuit of said second tube, said first and saidsecond tubes being arc-discharge tubes having their grids negativelybiased to cutoff, said third tube bein a high perveance vacuum tubehaving its grid positively biased so that it is normally of lowimpedance, means to apply a sharp positive pulse to the grid of saidfirst tube to render it conducting whereby space-current will flowthrough said load circuit, an adjustable resistance-capacitytime-constant circuit for transmitting the voltage drop across said loadcircuit to the grid of said second tube and render it conducting wherebyspace-current will flow through said resistor, a blocking oscillatorcircuit coupled to the output of said resistor for generating a sharpnegative pulse for each pulse of voltage across said resistor, and meansfor applying said negative pulseto the grid of said third tube to renderit non-conducting thereby interrupting the space-current flow throughall of said tubes.

3. An electronic circuit comprising at least first, second and thirdelectron tubes, said first and second tubes having their space-currentpaths connected in parallel and connected to a source of space-currentin series with the spacecurrent path of said third tube, an impedance inthe cathode circuit of said second tube, said first and second tubesbeing normally biased to render them non-conducting, means to rendersaid first tube conducting, whereby space-current will flow through saidfirst and third tubes, means including a time delay circuit responsiveto the output of said first tube to render said second tube conductingwhereby space-current will flow through said impedance, and meansresponsive to current flow in said impedance to render said third tubenon-conducting thereby interrupting the space-current flow through allof said tubes.

4. An electronic circuit comprising at least first, second and thirdelectron tubes, said first and second tubes having their space-currentpaths connected in parallel and connected to a source of space-currentin series with the spacecurrent path of said third tube, an impedance inseries with the space-current path of said second tube, said first andsecond tubes being normally non-conducting arc-discharge tubes, means torender said first tube conducting, whereby spacecurrent will flowthrough said first and third tubes, means including a time delay circuitresponsive to the output of said first tube to render said second tubeconducting whereby space-current will flow through said impedance, andmeans responsive to current flow in said impedance to render said thirdtube non-conducting thereby interrupting the space-current fiow throughall of said tubes.

5. An electronic circuit comprising at least first, second and thirdelectron tubes, said first and second tubes having their space-currentpaths connected in parallel and connected to a source of space-currentin series with the spacecurrent path of said third tube, an impedance inthe cathode circuit of said second tube, said first and second tubesbeing normally non-conducting arc-discharge tubes, means to render saidfirst tube conducting, whereby space-current will flow through saidfirst and third tubes, means including a time delay circuit responsiveto the output of said first tube to render said second tube conductingwhereby space-current will fiow through said impedance, and meansresponsive to current fiow in said impedance to render said third tubenon-conducting thereby interrupting the space-current flow through allof said tubes.

(5. An electronic circuit comprising at least first, second and thirdelectron tubes, said first and second tubes having their space-currentpaths connected in parallel and connected to a source of space-currentin series with the spacecurrent path of said third tube, a load circuitconnected in series with the space-current paths of said first and thirdtubes, an impedance in the output circuit of said second tube, saidfirst and said second tubes being arc-discharge tubes normally atcute-ff, said third tube being biased to render it normally or lowimpedance, means to render said first tube conducting wherebyspacecurrent will flow through said first and third tubes and said loadcircuit, a time delay circuit responsive to said space-current flow torender said second tube conducting whereby space-current will fiowthrough said impedance, means coupled to the output of said impedancefor generating a sharp pulse for each change of voltage across saidimpedance, and means for applying said sharp pulse to said third tubetorender it 5 non-conducting thereby interrupting the spacecurrent flowthrough all of said tubes.

7. An electronic circuit Comprising at least first, second and thirdelectron tubes, said first and second tubes having their space-currentpaths connected in parallel and connected to a source of space-currentin series with the spacecurrent path of said third tube, a load circuitconnected to said first tube, a resistor in the cathode circuit or" saidsecond tube, said first and said second tubes being arc-discharge tubesnormally at cutcfi, said third tube being a vacuum tube biased so thatit is normally of low impedance, means to a pulse to said first tube torender it conducting whereby space-current will flow through said loadcircuit, a time delay circuit for transmitting the voltage drop acrosssaid load circuit to said second tube to render it conducting wherebyspace-current will flow through said resistor, a pulse generator keyedby the output of said resistor for generating a sharp pulse for eachchange of voltage across said resistor, and means for applying saidsharp pulse to said third tube to render it non-conducting therebyinterrupting the space-current flow through all of said tubes.

8. An electronic network comprising at least first, second and thirdgrid-controlled electron tubes, said first and second tubes having theirspace-current paths connected in parallel and connected to a source ofspace-current in series with the space-current path of said third tube,a load circuit connected in the cathode circuit of said first tube, aresistor in the cathode circuit of said second tube, said first and saidsecond tubes having their grids negatively biased to cutoff, said thirdtube having its grid positively biased so that it is normally of lowimpedance, means to apply spaced pulses to the grid of said first tubeto render it conducting whereby spacecurrent will fiow through said loadcircuit, .a time delay circuit for transmitting the voltage drop acrosssaid load circuit to the grid of said second tube to render itconducting whereby space-current will flow through said resistor, apulse-forming circuit coupled across said resistor for generating asharp pulse for each pulse of voltage across said resistor, and meansfor applying said sharp pulse to the grid of said third tube to renderit non-conducting thereby interrupting the space-current flow throughall of said tubes.

9. The invention set forth in claim 8, wherein the total time delay ofsaid electronic network is greater than the interval between said spacedpulses.

10. The invention set forth in claim 8, wherein the total time delay ofsaid electronic network is greater than the duration of said spacedpulses but less than the intervals therebetween.

11. The invention set forth in claim 8, wherein the total time delay ofsaid electronic network is less than the duration of said spaced pulses.

JACOB L. RECTOR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,102,951 Hackenberg Dec. 21,1937 2,303,453 Gulliksen Dec. 1, 1942

